CHANGES IN BONE-MINERAL DENSITY OF THE DISTAL FEMUR FOLLOWING UNCEMENTED TOTAL KNEE ARTHROPLASTY

The aim of the study was to quantitate changes in bone mineral density (BMD) in the distal femur following uncemented porous-coated total kn ee arthroplasty. Eight patients with total knee arthroplasties (PCA Pr imary, Howmedica, Rutherford, NJ) (female:male ratio, 6:2, mean age, 7 0 years; range, 51-77 years) were scanned by dual-photon absorptiometr y within 3 months after surgery and at 2 years. An average decrease of 36% (P = .01) was found in BMD behind the anterior flange of the femo ral prosthesis. Proximal to the fixation pegs, BMD increased by 22% (P = .12), but behind the posterior flange of the femoral component, BMD remained unchanged (P = .53). Stress shielding anteriorly in the dist al femur occurred in all patients examined 2 years after surgery, and the increase in BMD proximal to the fixation pegs was probably a resul t of increased and altered mechanical loading.